WASHINGTON — The Canadian election Monday ousted a strong supporter of the Keystone XL pipeline. And it brought into office another strong supporter of the Keystone XL pipeline.

The new Canadian premier, Liberal Party leader Justin Trudeau, has supported the construction of the controversial Keystone XL pipeline, as well as TransCanada’s proposed $12 billion Energy East pipeline, both of which would carry bitumen from Alberta’s vast oil sands to ports and world markets.

Trudeau has said the pipelines should be important parts of a national infrastructure program he supports. But at the same time, he advocates the adoption of a national plan to reduce greenhouse gas emissions. Environmental groups say the two positions are incompatible.

Trudeau also favors an end to fossil fuel subsidies, and he has extolled the virtues of carbon taxes, though he has said decisions about that might be best left to provincial governments. Many supporters of a more aggressive climate policy say Canada’s federal government needs to take leadership on that front.

It is unclear how Trudeau’s election will affect U.N. climate talks in Paris later this year, but it could alter the dynamics and make it easier to secure the kind of stricter agreement the U.S. and Europe have been advocating. Canada’s outgoing Prime Minister Stephen Harper resisted the idea of more ambitious carbon pact and renounced the nation’s commitments under the Kyoto Protocol. Still, Trudeau has suggested he would consult with top provincial officials before revising Canada’s overall climate goals, an approach that would likely delay any new comprehensive strategy until after the U.N. negotiations.

Trudeau’s support for oil sands pipelines and oil sands development played well in Alberta, where low oil prices have delayed the expansion of oil sand (or tar sand) extraction and where unemployment has climbed to nearly 7 percent, the highest in four years. But environmental groups say that the oil sands extraction — which requires more energy to exploit and therefore emits more greenhouse gases in the process — undercuts climate change efforts and mars Alberta’s unspoiled unique boreal forests.

“Justin Trudeau needs to know that you can’t deal with climate change and build more tar sands pipelines, especially when those pipelines don’t get any sort of climate review,” Cameron Fenton, Canadian Tar Sands Organizer with 350.org, said on the group’s Web site.

The Keystone XL pipeline would carry oil sands crude from northern Alberta to the southern border of Nebraska, where it would connect with other legs of the Keystone network leading to Port Arthur. Much of the oil would then be exported.

The pipeline has become a symbol and litmus test for American politicians’ position on climate change. The Obama administration has been studying the proposal, which was first submitted seven years ago.